The invention relates to a circuit configuration and a method for supplying voltage to an integrated circuit through a pad that is also used to configure the integrated circuit.
One of the most important goals in developing integrated circuits is to save valuable chip area. The smaller an integrated circuit, the higher the effective yield per wafer during fabrication. The chip housing into which the integrated circuit is incorporated forms a further cost factor. In this case, the type of housing is determined principally by the number of pads or terminals of the integrated circuit. In order to be able to use an inexpensive chip housing, therefore, endeavors are made to save pads during the development of integrated circuits.
In complex integrated circuits such as microprocessors or complicated microcontrollers, many of the pads present are provided exclusively for voltage supply purposes. If some of the pads provided for voltage supply purposes are dispensed with in favor of a less expensive housing, however, there is an increase in the risk of functional disturbances because of a possibly excessively low current supply via the remaining pads for the voltage supply. In addition, the chip becomes more sensitive to external interference because of EMC (electromagnetic compatibility). Furthermore, the chip itself radiates to a greater extent and can thus interfere with other chips or components in an electronic system. Functional pads or pads that are provided for testing can rarely be dispensed with.
It is accordingly an object of the invention to provide a circuit for supplying voltage to an integrated circuit and a method for supplying the voltage to the integrated circuit which overcome the above-mentioned disadvantages of the prior art apparatus and methods of this general type.
In particular, is an object of the invention to provide a circuit and a method that enables a circuit designer to save pads when supplying voltage to an integrated circuit, without accepting the disadvantages mentioned in the introduction.
With the foregoing and other objects in view there is provided, in accordance with the invention, a circuit that includes: an integrated circuit having a plurality of voltage supply lines, a pad for configuring the integrated circuit, and a Schmitt trigger having an input connected to the pad; and a circuit configuration for supplying voltage to the integrated circuit through the pad. The circuit configuration includes switches in which each one of the switches is for connecting the pad to a respective one of the plurality of the voltage supply lines. The circuit configuration includes a control circuit for switching the switches on and off. The control circuit is controlled by at least one on-chip control signal.
In accordance with an added feature of the invention, the circuit configuration includes driver circuits; the control circuit switches each one of the switches on and off with a respective one of the driver circuits; and the driver circuits has inputs connected to the pad.
In accordance with an additional feature of the invention, the circuit configuration includes resistors; the driver circuits have outputs; and each one of the outputs of the driver circuits is connected to one of the plurality of the voltage supply lines by a respective one of the resistors.
In accordance with another feature of the invention, the plurality of the voltage supply lines include a first voltage supply line and a second voltage supply line; the switches include a first switch and a second switch; the first switch connects the pad to the first voltage supply line; and the second switch connects the pad to the second voltage supply line.
In accordance with a further feature of the invention, the switches are MOS transistors.
In accordance with a further added feature of the invention, the switches are bipolar transistors.
In accordance with a further additional feature of the invention, the circuit configuration includes a third transistor having a load path and a control terminal; the load path of the third transistor connects the pad to a line selected from the group consisting of the first voltage supply line and the second voltage supply line; and the control terminal of the third transistor is connected to a line selected from the group consisting of the first voltage supply line and the second voltage supply line.
With the foregoing and other objects in view there is also provided, in accordance with the invention, a method for supplying voltage to and configuring an integrated circuit via a pad. The method includes steps of: providing an integrated circuit having a plurality of voltage supply lines, a pad for configuring the integrated circuit, and a Schmitt trigger having an input connected to the pad; providing a circuit configuration for supplying voltage to the integrated circuit through the pad; providing the circuit configuration with switches; providing each one of the switches for connecting the pad to a respective one of the plurality of the voltage supply lines; providing the circuit configuration with a control circuit for switching the switches on and off; controlling the control circuit with at least one on-chip control signal; and providing a voltage at the pad to supply the voltage to one of the plurality of the voltage supply lines of the integrated circuit and to configure the integrated circuit.
The invention relates to a circuit configuration for supplying voltage to an integrated circuit via a pad. The pad is connected to the input of a Schmitt trigger on the integrated circuit and is provided for configuring the integrated circuit. The integrated circuit has a multiplicity of voltage supply lines for voltage supply purposes. According to the invention, the pad is connected to a respective voltage supply line via a respective switch and the switches are switched on or off by a control circuit that is controlled by at least one on-chip control signal.
In many integrated circuits, in particular in ones that are highly complex, some pads are provided for configuring the integrated circuit. For example, these pads can be used to set a specific operating mode or to switch the integrated circuit into a test mode for testing specific modules. In an electronic system, these pads are continuously connected to a supply voltage of the integrated circuit during the operation of the integrated circuit. Accordingly, these pads which are actually provided for configuring the integrated circuit can also be used for voltage supply purposes. The actual function of the pad is not impaired thereby, but rather is preserved. However, the integrated circuit can be supplied, via the pad, only with the voltage that is present for configuration purposes. To that end, according to the invention, switches that connect the pad, in each case, to one of the supply voltages of the integrated circuit are provided on the integrated circuit. This advantageously means that pads for the supply voltage can be saved.
Preferably, the control circuit switches the switches on or off via a respective driver circuit. The inputs of the driver circuits are directly connected to the pad. To that end, the control circuit blocks or unblocks the driver circuits that use a voltage present at the pad for switching the switches.
The outputs of the driver circuits are preferably connected to one of the supply voltages on the integrated circuit via a respective resistor. This effects a pull function, so that, even when the driver circuits are turned off, the driver outputs are at a defined potential and the switches are switched on or off in a defined manner.
In particular, the switches are embodied as power transistors. In order to supply the integrated circuit with sufficient current via the pad, power transistors are particularly suitable for a high current flow via the pad. By contrast, simple transistors would only limit the possible supply current via the pad.
In one embodiment of the invention, the integrated circuit preferably has a first supply voltage line, a second supply voltage line, a first switch, and a second switch. The first switch connects the pad to the first supply voltage line and the second switch connects the pad to the second supply voltage line. Nowadays, many integrated circuits are supplied with two supply voltages, for example 5 V and 0 V. In this case, precisely two switches are required for embodying the invention, which switches connect the pad for example to 5 V and 0 V.
The pad is preferably connected to the first supply voltage and to the second supply voltage via the load path of a third transistor and the load path of a fourth transistor, respectively. The control terminal of the third transistor is connected to the second supply voltage and the control terminal of the fourth transistor is connected to the first supply voltage. In this embodiment of the invention, xe2x80x9cfloatingxe2x80x9d of the pad is avoided and the pad is at a defined potential as long as no external voltage is present.
In particular, the first and second transistors are embodied as MOS transistors. This embodiment is advantageous when the integrated circuit is fabricated using purely MOS technology. As an alternative, the first and second transistors may be embodied as bipolar transistors. If the integrated circuit is fabricated using BiCMOS technology, this embodiment is appropriate since bipolar transistors are particularly suitable as current sources and cope with very large currents.
The invention furthermore relates to a method for supplying voltage to and for configuring an integrated circuit using a pad at which a voltage is present. The voltage on the pad is used both for configuring the integrated circuit and for providing a supplying voltage to the integrated circuit.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a circuit configuration for supplying voltage to an integrated circuit via a pad, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.